Growth behavior and insulation property of the oxide layer during micro-arc oxidation of aluminium in “soft” regime condition

摘要

Abstract In this work, micro-arc oxidation was applied to fabricate a high voltage resistance Al2O3-based ceramic coating on the surface of aluminum alloy. The microstructure and insulating properties of the coatings were characterized by XRD, SEM and breakdown voltage testers. The growth behavior and insulation property of the oxide layer in “soft” regime conditions of micro-arc oxidation were determined. The relative contents of α-Al2O3 increased with “soft” plasma discharge time. The soft plasma discharge brought about a tendency of the micro-arc oxide coating to grow outward, further repairing the coating defects and yielding a denser coating layer with improved corrosion protection. Due to the presence of negative currents, the thickness of the whole layer increased, while the inner layer became denser and thicker as a consequence of soft sparks, favoring an increase in the density of the bulk coating layer. The breakdown voltage reached values above 1000 V after 20 min of soft plasma discharge, improving the of micro-arc oxidation coating insulation properties. The oxide layer is thus proposed as a potential candidate for insulation shielding of etching equipment.